//Haskell
main = print $ foldl eval [] $ words "3 10 * 20 5 / +" -- 34

eval (x:y:xs) "+" = y+x : xs
eval (x:y:xs) "-" = y-x : xs
eval (x:y:xs) "*" = y*x : xs
eval (x:y:xs) "/" = y`div`x : xs
eval  xs      dig = (read dig):xs